1. Field of the Invention
The present invention relates to a process for producing an aromatic aldehyde compound without hydrogen-reduction under high pressure and having advantages of low cost, high efficiency and low contamination.
2. Description of the Prior Arts
Synthetic aromatic compound is largely used in industries for producing perfumes or essence oils, which are useful for articles for daily use, such as soap, detergent, cosmetics and so on. Common synthetic aromatic compounds include aromatic aldehyde compounds, for example, lysmeral, floralozone and so on. Industrial production of aromatic aldehyde compounds is first developed by Givaudin Corporation. However, current techniques for industrial production of aromatic aldehyde compounds still have several problems.
A current process for producing an aromatic aldehyde compound is shown in Scheme I, wherein production of 4-tert-butyl-phenyl-formaldehyde is critical. The final step of the process requires hydrogen-reduction with palladium on carbon catalyst under high pressure. Use of noble metal as catalyst results in high cost of production. Patent NO. WO2007045641 owned by Badische Anilin- and Soda-Fabrik Corp. (BASF) aims at improving the final step for hydrogen-reduction of the above process. However, the reaction pressure is so high as 30 Bar, leading to difficulties in its industrialization.

Givaudin Corporation discloses a process for producing an aromatic aldehyde in Bull. Soc. Chem. Fr., p 1194 in 1961, as shown in Scheme II. The process utilizes great amounts of TiCl4 and BF3-Et2O as catalyst. However, it has a yield less than 10%. Moreover, one of the raw materials, 2-methylpropenal, is rare and difficult to be obtained, and TiCl4 is easy to be hydrolyzed. Therefore, the process cannot be industrialized and will cause three wastes, that is, waste water, waste gas and industrial residue, leading to environmental pollutions.

DE2627112 discloses a process for producing an aromatic aldehyde compound as shown in Scheme III. Although its yield is higher than 80%, one of the raw materials, 2-methylpropenal, is extremely rare and high-priced, resulting in the limitation of the process in industrial application. A process published in Journal of Molecular Catalysis A: Chemical, 231(1-2), 61-66 (2005) is a modification of the above process and achieves a theoretical production rate of 95%. However, the modified process requires use of 4-tert-butyliodobenzene as raw material, rare elements as catalyst, and ion liquid for reaction, and has a reaction time more than 24 hours, which leads to its low efficiency and failure in industrial application.

DE2851024 discloses a process for producing an aromatic aldehyde compound, as shown in Scheme IV. The process requires a great amount of AlCl3, and has problems of three wastes and corrosion of manufacturing equipments. Furthermore, the known Vilsmeier reaction also has problems of three wastes and has a yield of only 35%. A process published in Organic Preparations and Procedures International, 14(1-2), p 2-20 is a modification of the above process. However, the modified process still requires hydrogen-reduction as a final step and utilizes noble metal as catalyst, contributing to its high production cost.

To overcome the shortcomings, the present invention provides a process for producing an aromatic aldehyde compound that requires no hydrogen-reduction under high pressure with expensive and complicated manufacturing equipments and will not cause pollution to environment to mitigate or obviate the aforementioned problems.